Method and apparatus for transporting particulate material to a metallurgical furnace



3,318,686 T I CULATE 2 Sheets-Sheet 2 Filed July 2, 1963 INVENTOR UnitedStates Patent METHOD AND APPARATUS FOR TRAN SPORTING PARTICULATEMATERIAL TO A METALLURGI- CAL FURNACE Elwood V. Schulte, Pittsburgh, Pa,assignor to Koppers Company, Inc., a corporation of Delaware Filed July2, 1963, Ser. No. 292,239

' 7 Claims. (Cl. 75-42) This invention relates to the construction andoperation of apparatus for transporting particulate material to ametallurgical furnace and more particularly to a method and apparatusfor transporting preselected quantities of coal particles through aplurality of conduits to the tuyere zone of a blast furnace.

Coke, the presently used blast furnace fuel, represents a substantialportion of the costs incurred in the ore reduction process. Numerousattempts have been made in the past to reduce the process costs byeither mixing a less expensive fuel with the charge and introducing themixture into the top of the blast furnace, or injecting a less expensivefuel into the tuyere or hearth zone of the blast furnace. Admixing lessexpensive fuel with the charge met with little success. The addition ofless expensive fuels to the charge presented operating difficulties inthat the less expensive fuels hampered the upward flow of blast gas anddid not adequately support the burden within the blast furnace.

From the over-all economic standpoint, introducing coal particles intothe tuyere zone of the furnace offers the most favorable incentives. Itis difficult, however, in injecting coal particles, to accuratelycontrol the quantity of the coal introduced into the fur-nace andcontrol the distribution of the coal particles in the various quadrantsof the blast furnace tuyere zone. Accurate quantitative control andcontrolled distribution of the coal particles are prerequisites toproper blast furnace operation.

It has been found that coal particles can be injected into the tuyerezone of a blast furnace by suspending the coal particles in a gas. Animproved rotary coal feeder has been suggested wherein the coalparticles are delivered from a feed bin under atmospheric pressure intoperipheral pockets of a rotary feeder wheel. The rotary feeder Wheelrotates within a casing and transfers the coal particles to apressurized gas stream. The gas is flowing at a sufficiently highvelocity to suspend the particles as a dilute phase fluidized unass. Ithas been suggested that individual rotary feeders and supply conduits beprovided for one or, at most, two injection ports in the side of theblast furnace. This type of installation requires a substantialinvestment in rotary coal feeders and conveying conduits to the blastfurnace.

It has now been found that it is possible to reduce the number of rotarycoal feeders and conveying conduits required to transport the samecoal-air mixture from a common feeder bin to the injection tuyerespositioned in the side Wall of the blast furnace. The coal-air mixtureis transported through a common conduit to a splitting device where themixture is divided into a plurality of separate streams. The separatestreams are conducted through individual supply conduits to therespective tuyeres. With this arrangement the number of coal feedersrequired for each installation is substantially reduced.

To maintain a smooth, continuous operation of the blast furnace it isnecessary that the quantity of coal introduced into the furnace beaccurately controlled. The coal furnishes the heat necessary to maintainthermal equilibrium in the blast furnace and further supplies the carbonmonoxide used for effecting the reduction of the ore to metallic iron.It is readily apparent if the quantity of coal introduced into the blastfurnace is not accurately controlled, erratic blast furnace operationwould result.

3,318,686 Patented May 9, 1967 Where a substantial number of coalfeeders are used to introduce the coal particles into separate supplyconduits, coordinated control of all the coal feeders is required. Ithas been found with the apparatus herein disclosed that accuratemetering of the total quantity of coal fed to the furnace is easilyobtained by regulating the flow through the primary conduit.

It has further been found to be highly advantageous to selectivelycontrol the flow of coal to certain of the tuyeres.

The conventional blast furnace is cylindrical in shape with tuyeresarranged circumferentially in the blast furnace Wall. Coal particles areinjected into the tuyere zone through all of the circumferentiallyspaced tuyeres. When, because of operating conditions present inside theblast furnace, it is desirable to reduce the quantity of coal injectedinto the tuyere zone of the furnace flow of coal particles throughcertain of the tuyeres is stopped.

The manner in which the various tuyeres are taken off stream is criticalin that the total quantity of coal particles fed to the blast furnaceshould be evenly distributed throughout the entire cross sectional areaof the tuyere zone. Otherwise, one section of the tuyere zone would havean excess of coal particles fed thereto and another section would havean insufficient amount of coal particles fed thereto. Unevendistribution of the fuel in the tuyere zone could result in uneventemperature gradients in the blast furnace. Uneven distribution of fuelcould further cause excess reducing gas to flow upwardly through onesection of the furnace and insufficient reducing gas to flow upwardlythrough another section of the furnace. Uneven distribution ofsuflicient quantities of fuel in the tuyere Zone would result in erraticblast furnace operation and an inferior metal product. The apparatusherein disclosed includes means for stopping the flow of particulatecoal to certain of the tuyeres when it is desired to reduce the amountof coal fed to the blast furnace. The selective control to the varioustuyeres of the blast furnace provides for uniform distribution of thecoal particles within the tuyere zone of the blast furnace.

Briefly, the invention includes a coal feeder that transfers preselectedquantities. of coal to a gas stream. The gas stream is flowing at asufficiently high velocity to suspend the coal particles therein andconvey the suspended coal particles as a fluidized mass. The gas streamwith the suspended coal particles is transported through a commonconduit to divider means where the coal is split into a plurality ofstreams containing substantially equal amounts of coal. The streams aretransported through separate conduits to circumferentially spacedtuyeres in the blast furnace side wall. Valve means are included toclose certain of the supply conduits and thereby channel the coal toselected sections of the tuyere zone. Means are. provided for purgingthe supply conduits with a purge gas after the flow of coal particlestherethrough has stopped. The gas used to purge the supply conduits maybe either air or an inert gas. Throughout the specification the purgegas will be designated an inert gas. It should be understood, however,that air can also be used as the purge gas. The velocity of the gasstream and the amount of coal fed to the gas stream may be regulated tofurther control the amount of coal periodically fed to the blastfurnace. It is now possible with the herein disclosed invention tosupply preselected quaitities of coal to preselected portions of thetuyere zone for uniform distribution of the coal particles in the blastfurnace.

Accordingly, an object of this invention is to provide a method andapparatus for supplying coal praticles to a substantial number of blastfurnace tuyeres from a single coal feeder.

Another object is to provide a method and apparatus for accuratelycontrolling the quantity of coal transported to the tuyere zone of ablast furnace and for delivering the coal particles to the blast furnacein a manner that the coal particles are uniformly distributed within theblast furnace tuyere zone.

These and other objects and advantages of this invention will be morecompletely disclosed and described in the following specification, theaccompanying drawings and the appended claims.

In the accompanying drawings there is shown for purposes of illustrationone form which the invention may assume in practice.

In the drawings:

FIGURE 1 is a schematic representation of a transportation anddistribution means for particulate coal that is transported to a blastfurnace.

FIGURE 2 is a schematic representation of the distributors for thepulverized coal.

Referring to FIGURE 1, there is illustrated a coal storage hopper wit-ha conduit 12 extending therefrom and to a coal feeder 14. The storagehopper 10 is preferably arranged to supply particulate coal by gravitythrough conduit 12 to the coal feeder 14. A variable speed motor 16 isarranged to drive the coal feeder 14 at preselected speeds.

The coal feeder 14 may be a positive displacement type of coal feeder asis described in Patents 2,750,233 and 2,750,234. The coal feederdescribed in the abovementioned patents includes a casing enclosing agear shaped rotor. Coal is fed radially to the gear shaped rotor atatmospheric pressure and the openings or pockets in the rotor are filledwith particulate coal. The rotor rotates through approximately 180 wherea conduit, arranged substantially parallel to the axis of the rotor,supplies pressurized air to the coal feeder casing. The air ejects thecoal from the pockets aligned with the conduit and conveys the coal in afluidized state from the coal feeder to the blast furnace at apreselected pressure and velocity. The coal particles are thus fluidizedin the pressurized air and are transported to the blast furnace in thisfluidized state.

A blower or compressor 18 has its outlet conduit 20 connected to thecoal feeder 1'4 and is arranged to provide the pressurized air to coalfeeder 14 to fluidize the particulate coal and conduct the particulatecoal in a fluidized state from the coal feeder 14 to the main conduit22. The compressor 18 has a variable speed motor 24 associated therewithto provide air at a preselected pressure for the coal feeder 14. Thus,both the coal feeder 14 and the compressor 18 may be regulated to supplya preselected quantity of particulate coal and air in a fluidized state.

In FIGURE 1 a plan view of the system employed to distribute the coalparticles in the air carrier to blast furnace 25 is schematicallyillustrated. The fluidized coal is preferably delivered to the existinghot blast tuyeres in the blast furnace. For example, the blast furnaceillustrated in FIGURE 1 has sixteen tuyeres numbered in a clockwisedirection 26 to 56 inclusive. The tuyeres 26-56 are arrangedsymmetrically about the blast furnace 25 and fluidized particulate coalmay be supplied to all or some of the tuyeres 26-56 as required by theconditions of the reduction process within the blast furnace 25.

In FIGURE 2 the distribution system for the fluidized coal isschematically illustrated in elevation. The main supply conduit 22 liftsthe fluidized coal upwardly through the upwardly extending portion ofmain conduit 22 and introduces the fluidized coal into a first splitteror distributor 58 indicated schematically by the inverted arrangement inthe main supply conduit 22. The splitter or distributor 58 is preferablythe type that will distribute equal amounts of fluidized coal into twobranch conduits.

Two equal streams of fluidized coal are delivered from main conduit 22by means of splitter 58 to a pair of primary branch conduits 60 and 62.Adjacent the splitter 58 each of the primary branch conduits 60 and 62has a control valve 64 and 66 positioned therein. Downstream of controlvalves 64 and 66 the primary branch conduits 60 and 62 have inert gasinlet conduits 68 and 70 connected thereto. The inert gas conduits 68and 70 have normally closed control valves 72 and 74 that control theflow of inert gas therethrough. A suitable supply of inert gas atpreselected pressures is provided for the inert gas conduits 68 and 70.

The primary branch conduit 60 conducts one half of the fluidizedparticulate coal supplied to main conduit 22 from coal feeder 14 to asplitter or distributor 76 which is similar to the distributor orsplitter 58 in main conduit 22.

The splitter or distributor 76 further divides the fluidized coal inprimary branch conduit 60 into substantially equal amounts anddistributes the equal amounts to secondary branch conduits 78 and 80.Valves 82 and 84 are positioned in secondary branch conduits 78 anddownstream of the splitter 76 and are arranged to close the respectivesecondary branch conduits 78 and 80. The secondary branch conduit 78 hasan inert gas inlet conduit 86 connected thereto downstream of the valve82. A normally closed control valve 88 is positioned in inert gasconduit 86 and controls the flow of inert gas through conduit 86 to thesecondary branch conduit 78.

The primary branch conduit 62 terminates at a distributor or splitter 90which divides the fluidized coal stream flowing through primary branchconduit 62 into two equal streams which flow into secondary branchconduits 92 and 94. Both secondary branch conduits 92 and 94 havecontrol valves 96 and 98 therein arranged to control the flow throughthe respective secondary branch conduits. An inert gas inlet conduit 100is connected to secondary branch conduit 94 downstream of valve 98 andhas a valve 102 therein arranged to control the flow of inert gas intothe secondary branch conduit 94.

The secondary branch conduit 78 terminates at a splitter device 104.Tertiary branch conduits 106 and 108 are connected to the splitterdevice 104 and are arranged to receive equal amounts of fluidizedparticulate coal from secondary branch conduit 78. Both tertiary branchconduits 106 and 108 include valves 110 and 112 to control the flow offluidized coal therethrough. The tertiary branch conduit 106 has aninert gas inlet conduit 114 connected thereto downstream of valve 110. Acontrol valve 116 is positioned in inert gas inlet conduit 114.

The secondary branch conduit 80 similarly terminates in a splitterdevice 117 and supplies equal amounts of fluidized particulate coal totertiary branch conduits 118 and 120. Valves 122 and 124 are positionedin tertiary conduits 118 and to control flow therethrough. An inert gasinlet conduit 126 is connected to tertiary conduit 118 downstream ofvalve 122 and includes a control valve 128.

Secondary branch conduit 92 similarly terminates in a splitter device130 and equal amounts of fluidized coal are conducted from secondarybranch conduit 92 to tertiary branch conduits 132 and 134. Valves 136and 138 are positioned in tertiary branch conduits 132 and 134 andcontrol flow therethrough. An inert gas inlet conduit 140 is connectedto conduit 134 downstream of valve 138 and includes a control valve 142.

The secondary branch conduit 94 is connected to a splitter device 144and equal amounts of fluidized particulate coal are conveyed fromsecondary branch. conduit 94 to tertiary branch conduits 146 and 148.The tertiary branch conduits 146 and 148 have valves 150 and 152therein. Tertiary branch conduit 148 has an inert gas inlet conduit 154connected thereto downstream of the valve 152. A control valve 156 ingas conduit 154 controls flow of inert gas through conduit 154 totertiary branch conduit 148.

All of the tertiary branch conduits 106, 108, 118, 120, 132, 134, 146,and 148 are connected at their discharge ends to splitter devices whichsupply equal amounts of fluidized particulate coal to supply conduitsconnected to the branches of the respective splitter devices. Forconvenience the latter splitter devices are all indentified by thenumeral 158. The supply conduits are numbered in even numbersconsecutively from left to right as supply conduits 160490. Therespective tuyeres supplied by the supply conduit are designateddirectly below the respective supply conduits in FIGURE 2. Supplyconduit 160 provides fluidized particulate coal for tuyere 26 and supplyconduit 162 supplies fluidized coal for tuyere 42. It should be notedthat the tuyeres supplied from a common tertiary conduit arediametrically opposed as viewed in FIGURE 1. For example, tuyere 26 isdiametrically op posed from tuyere 42 and both tuyeres 26 and 42 aresupplied from tertiary conduit 106 through supply conduits 160 and 162.A similar arrangement is provided for all of the remaining tuyeres andsupply conduits. The arrangement whereby a common tertiary branchconduit supplies a pair of diametrically opposed tuyeres is readilyapparent in FIGURE 1. Thus, the closing of a valve in one of thetertiary conduits stops the flow of fluidized coal to a pair ofdiametrically opposed tuyeres.

It should also be noted that the tertiary branch conduit 148 suppliesfluidized particulate coal to a pair of tuyeres that are arranged inapproximately transverse diametrical relation to the pair of tuyeressupplied by tertiary conduit 106. With this arrangement it is possibleto stop the flow of particulate coal to four tuyeres spaced 90 from eachother by closing two valves. The relationship of the various supplyconduits and tertiary branch conduits is clearly illustrated in the planview schematic representation in FIGURE 1. It should be understood thatif a blast furnace has a lesser or greater number of tuyeres, thedistributor and control arrangement illustrated in FIGURES 1 and 2 couldbe modified to provide for the distribution and operation hereinafterdescribed.

The various conduits or headers are preferably sized to provide thefollowing conditions. To suitably transport the particulate coal throughthe various conduits in the distribution system, the coal-air mixturemust remain fluidized as it is transported from the coal feeder 14through the main conduit. The velocity of the air and coal and the ratioof air and coal in the main conduit 22 must be at least suflicient tomaintain the coal in a fluidized state. For exemplary purposes, it willbe assumed that the maximum amount of coke that will be replaced in theblast furna-ced by the coal would be 30 percent of the total coke usedin the ore reduction process. Thus, when 15 percent of the coke is beingreplaced by coal, the velocity in the main conduit 22 between coalfeeder 14 and the primary branch conduits 60 and 62 will be such that itis safely above the velocity required to keep the coal in a fluidizedstate. If the full 30 percent replacement of coke is desired, then thevelocity of the coal-air mixture in the main conduit will be increasedsubstantially above the minimum designated to maintain the coal in afluidized state.

To supply the maximum amount of coal to the blast furnace, all thevalves in the primary, secondary, and tertiary branch conduits areopened. All the valves in inert gas conduits are closed. If it isdesired to reduce the amount of coal fed to the blast furnace withoutshutting off any of the flow to any of the tuyeres, the rate of feed ofcoal through the coal feeder 14 and the amount of air supplied to thecoal feeder 14 is reduced to maintain a nonexplosive coal mixture andretain the coal in a fluidized state. A nominal air velocity in thepipelines should be kept above a minimum of 25 feet per second duringoperation. The coal feeder 14 and compressor 18 can be regulated by thevariable speed motors 16 and 24 to continually reduce the rate of coalflow and air velocity until approximately 15 percent of the coke wouldbe replaced by particulate coal fed into the blast furnace through thetuyeres. Any further reduction in the .air flow through the pipelinewould result in the deposit of coal particles in the various conduitswith ultimate plugging of the supply conduits.

If it is desired to further reduce the amount of coal fed to the blastfurnace, the rate of feed of the coal from feeder 14 can be furtherreduced, but the air velocity must not be reduced below a predeterminedminimum. The further reduction in the rate of coal feed to the airstream results in a more dilute phase fluidized stream with a suflicientair velocity to maintain all the coal particles suspended in the airstream. It is therefore readily apparent from an operability standpointwhy it is necessary to maintain the coal particles in a dilute phasefluidized state while the particles are being transported from the coalfeeder 14 to the blast furnace 25.

If it is desired to reduce the coal flow beyond the 50 percent reductionby the coal feeder 14 and compressor 18, or if it is desired to stop theflow of coal to certain sections of the blast furnace tuyere zone, thevalve in tertiary conduit branch 106 is closed and valve 116 in inertgas conduit 114 is simultaneously opened. The closing of valve 110 stopsthe flow of fluidized coal to supply conduits 160 and 162 and hence totuyeres 26 and 42 located on diametrically opposite positions in theside wall of blast furnace 25. The valve 116 in inert gas supply conduit114 is opened to purge the tertiary conduit 106 and supply conduits 160and 162. As soon as the conduits are purged of coal and air downstreamof valve 110, the flow of inert gas through conduit 114 may be eithercontinued or discontinued depending upon the need to keep the conduitscool and in working condition. If suitable cooling means is provided forthe conduits adjacent the respective tuyeres, the valve 116 may beclosed. Suitable control means can be provided to simultaneously controlthe coal feeder 14 and the compressor 18 to either change the coal andair ratio or decrease the rate of feed of both the coal and air to themain conduit 22. It should be understood, however, that the velocity ofthe mixture flowing through the conduit 22 should be sufficiently highto maintain the coal particles in a fluidized state.

If a further decrease in the coal rate to the blast furnace 25 isdesired, or if it is desired to stop the flow of coal to other tuyeres,the tuyeres 34 and 50, which are 90 removed from tuyeres 26 and 42, aretaken off stream. To take tuyeres 34 and 50 off stream the valve 152 isclosed in tertiary branch conduit 148 and the valve 156 in inert gasconduit 154 is opened to purge the tertiary conduit 148 and the supplyconduits 190 and 192. The coal feeder 14 and compressor 18 are adjustedto reduce the amount of coal introduced into the blast furnace.

If a still further decrease in coal is desired, tuyeres 30 and 46 aretaken out of service. Tuyeres 30 and 46 are 45 removed from tuyeres 26,42 and tuyeres 34 and 50 previously taken off stream. The valve 122 intertiary conduit 118 is closed and the conduit 118 and supply conduits170 and 172 are purged by means of an inert gas flowing through conduit126. If it is desired to remove additional tuyeres from service, tuyeres54 and 38 which are also 45 removed from tuyeres 26, 42, and tuyeres 50,34 are removed from service. The valve 138 in tertiary branch conduit134 is closed and valve 144 in inert gas conduit is opened to purgetertiary conduit 134 and supply conduits 182 and 184.

Thus, the flow of coal to the blast furnace 25 has been reduced toone-fourth of its original maximum by first reducing the rate of coalflowing through the main supply conduit 22 and also by shutting offeight of the sixteen individual supply conduits feeding the individualtuyeres. At this point valves 110, 152, 122 and 138 are closed andvalves 112, 124, 136, and are open.

To shut off additional tuyeres, the next tuyeres preferably deactivatedare 28 and 44. To stop the flow of coal through tuyeres 28 and 44, thevalve 82 in secondary branch conduit 78 is closed. It is preferable toclose valve 82 in secondary branch conduit 78 rather than valve 112 intertiary branch conduit 108 in order to prevent the deposition of coalin the secondary branch conduit 78. Automatically with the closing ofvalve 82, valve 88 in inert gas conduit 86 is opened to purge secondaryZ branch conduit 78, tertiary branch conduit 108 and supply conduits 164and 168. If desired, valve 110 in te rtiary branch conduit 106 may beopened so that the inert gas entering through conduit 86 will purge allconduits downstream therefrom. With the above discussed valves closed,two-thirds of the fluidized coal that is added to the blast furnace isflowing through the primary branch conduit 62 and one-third of the coalis flowing through the other branch conduit 60.

To stop the flow of coal through another pair of tuyeres, the valve 98in secondary branch conduit 94 is closed and valve 102 in inert gasconduit 100 is opened. The closing of valve 98 stops the flow of coal totuyeres 36 and 52. The inert gas entering through conduit 100 purges allconduits downstream therefrom.

With the valve 82 in secondary branch conduit 78 closed and valve 98 insecondary branch conduit 94 closed, one-eighth of the maximum amount ofcoal expected to be added to the blast furnace is being supplied theretoand is being distributed through the secondary branch conduit 80 andsecondary branch conduit 92.

The next tuyeres that are deactivated, if a further reduction in thenumber of active tuyeres is desired, are 32 and 48. Valve 64 in primarybranch conduit 60 is closed and valve 72 in inert gas conduit 68 isopened to purge all the conduits downstream of valve 64. Certain of thevalves downstream of valve 64 may be closed or, if desired, all valvesdownstream of valve 64 may be opened.

It is apparent the closing of valve 66 in primary branch conduit 62would close the last two remaining tuyeres, i.e., tuyeres 40 and e.However, in lieu of closing valve 66, the coal feeder 14 could bestopped when the entire coal feeding system is stopped. The compressor18 could be operated for a sufficient period of time to purge the mainsupply conduit 22 and the remaining conduits leading to the blastfurnace.

It should be noted that in proceeding to reduce the coal flow to theindividual tuyeres when the velocity of the coal-air mixture in theconduits decreases below a predetermined satisfactory velocity tomaintain the coal particles fluidized in the transport air, it becomesnecessary to increase the ratio of conveying air to coal to therebymaintain the desired velocities in these main supply and branchconduits.

As previously described, the initial reduction in the coal fed to theblast furnace 25 is accomplished by reducing the output from coal feeder14 and the gas volume and pressure from compressor 18 to an extent thatthe total maximum feed is reduced 50 percent. An alternative procedurewould be to maintain the coal feeder 14 and compressor 18 at thepreselected settings to supply sufiicient coal to replace percent of thecoke normally used in the ore reduction process. To reduce the amount ofcoal below the 30 percent ratio preselected tuyeres are taken out ofservice, preferably in the order previously discussed. Half of thetuyeres could be removed at the time that one-half of the rate of flowof coal is passing between the coal feeder 14 to the main supply conduit22. By suitable control means at the closing of valve 110, for example,the coal feeder 14 and compressor 18 would have their output reduced toslow the feeder to one-eighth and would reduce the flow of air fromcompressor 18 to one-eighth at the same time. In this manner the totalflow of coal to the blast furnace 25 would be reduced by one-eighth ofits maximum by closing valve 110 and simultaneously reducing the outputof coal from coal feeder 14 and, if desired, the output of air fromcompressor 18.

If further reduction in coal supplied to the blast furnace 25 is desiredby the present procedure, valve 152 in tertiary supply conduit 148 wouldbe closed and the flow from feeder 14 and compressor 18 would be furtherreduced one-seventh. The reduction in both the supply of coal and air tothe main supply conduit would continue in this order until the rateshave been reduced to a point approaching the minimum velocity requiredto maintain the coal particles suspended in the air carrier. From thispoint the ratio of air to coal could be gradually increased as the flowof coal to additional tuyeres is stopped in order to maintain thereduced quantity of coal in a fluidized state as it travels from thefeeder 14 through the main conduit 22. A velocity of between 10 feet persecond and feet per second is required to properly remove the coalparticles from the rotor ports in coal feeder 14. The various conduitswould preferably be sized to give preferred velocities between 20 and 50feet per second.

The minimum air velocity required to carry coal particles is a variablequantity which varies exponentially with the mass flow rate of coal,with the air density Within the pipe at upstream temperature andpressure conditions, and with the coal size. At a given coal rate, themass flow rate is a function of the pipe diameter. The air density beinga function of pressure would vary with the blast furnace pressure andthe friction drop in the transfer line. The friction drop varies withpipe length, air velocity and coal velocity. The minimum air velocityis, therefore, highly dependent upon the characteristics of theparticular system.

The air velocities should be such that the coal particles will not dropfrom suspension in the main conduit 22. Because of the expansion of theair as it progresses further through the system the velocities shouldincrease with progression toward the blast furnace provided that thebranch lines are sized correctly.

A sixteen tuyere furnace may produce about 1375 net tons of hot metalper day. At an assumed coke rate of 1500 pounds per net ton hot metalthe coke consumed per hour would be about 85,800 pounds. The coal ratefor 30 percent coke replacement would be about 25,750 pounds per hourand at a 5 percent replacement would be about 4,300 pounds per hour.

Assuming a coal mass velocity of about 118 pounds per square foot persecond, the main conduit 22 could be fabricated from 3 /2 inch schedule80 pipe to transport coal at 25,750 pounds per hour for 30 percent cokereplacement. Assuming the coal particles have a mean diameter of about0.03 inch and assuming a pressure of 60 p.s.i.g. at the upstream end ofthe pipe and a temperature of 60 F., the minimum superficial airvelocity would be about 32 feet per second. About 600 s.c.f.m of airwould be used. The air-coal ratio would be about 1.45 s.c.f. per pound.

For 5 percent coke replacement, approximately 4,300 pounds of coal perhour is transported through the respective conduits. The mass velocitywould be about 19.4 pounds per square foot per second through the 3 /2inch main conduit 22. Because the friction drop is much less than at the30 percent coke replacement a line pressure of about 35 p.s.i.g. isassumed. The minimum superficial air velocity would be about 15 feet persecond and the total quantity of air would be about s.c.f.m. Thecoal-air ratio for a 5 percent replacement would be about 2.6 s.c.f. perpound.

It will be appreciated the above exemplary ratios are for minimum airvelocities and it should be understood to maintain the air velocitysufficiently high to prevent the coal particles from dropping out ofsuspension that the air velocities in the system would be above thoseset forth.

It should be understood that a suitable control means andinstrumentation may be provided to automatically control the respectivevalves in the distribution system and to simultaneously control theoutput of the coal feeder 14 and compressor 18.

Although the distributors are illustrated as splitting the stream ofcoal and air into two streams, it should be understood that suitablesplitters could be provided to split a single stream of coal and airinto a greater number of streams, such as four or eight streams of coal.

With the above arrangement it is now possible to feed a blast furnacefrom a single coal feeder. Where, hoW- ever, a blast furnace With agreater number of tuyeres is contemplated, it may be preferable toutilize a plurality of coal feeders.

According to the provisions of the patent statutes, the principle,preferred construction, and mode of operation of the invention have beenexplained, and what is now considered to represent its best embodimenthas been illustrated and described. However, it should be understoodthat, within the scope of the appended claims, the invention may bepracticed otherwise than as specifically illustrated and described.

I claim:

1. A method of injecting particulate coal particles into the tuyere zoneof a blast furnace which comprises (a) supplying particulate coal to acoal feeder,

(b) supplying a conveying air stream at superatmospheric pressure tosaid coal feeder,

(c) admixing said conveying air stream and said coal particles in saidcoal feeder to entrain coal particles in said conveying air stream as afluidized mass of said coal particles suspended in said conveying airstream,

(d) introducing said fluidized mass into a primary conduit at asuflicient velocity to maintain said coal particles suspended in saidconveying air stream,

(e) transporting said fluidized mass through said primary conduit to afirst spliter device,

(f) maintaining said particulate coal entrained in said conveying airstream as a fluidized mass in said first splitter device,

(g) dividing said fluidized mass in said splitter device into twosubstantially equal and separate streams,

(h) transporting each of said separate streams as a fluidized massthrough a separate secondary conduit to a second splitter device,

(i) maintaining said particulate coal entrained in said conveying airstream as a fluidized mass in said second splitter device,

(j) dividing each of said streams into two separate smallersubstantially equal substreams,

(k) transporting each of said substreams through a tertiary conduit tothe tuyere zone of said blast furnace, and

(l) introducing said separate substreams from said tertiary conduitsinto different quadrants of said blast furnace tuyere zone.

2. A method for injecting coal particles into the tuyere zone of a blastfur-nace as set forth in claim 1 which includes (a) interrupting theflow of at least one of said substreams while said other substreamscontinue to flow through their respective tertiary conduits therebycontrolling the introduction of said coal particles to more than onequadrant of said blast furnace tuyere zone.

3. A method of injecting coal particles into the tuyere zone of a blastfurnace as set forth in claim 1 which includes (a) interrupting the flowof at least one of said substreams While said other substreams continueto flow through their respective tertiary conduits thereby controllingthe introduction of said coal particles to certain quadrants of saidblast furnace tuyere zone, and

(b) introducing a gas into said tertiary conduits after the flowtherethrough has been interrupted to purge said tertiary conduits ofsaid coal particles.

4. A method of injecting particulate coal particles into the tuyere zoneof a blast furnace which comprises (a) supplying particulate coal to acoal feeder,

(b) supplying a conveying air stream at superatmospheric pressure tosaid coal feeder,

(c) admixing said conveying air stream and said coal particles in saidcoal feeder to entrain said coal particles in said conveying air streamas a fluidized mass of said coal particles suspended in said conveyingair stream,

(d) introducing said fluidized mass into a primary conduit at asufficient velocity to maintain said coal particles suspended in saidconveying air stream,

(e) transporting said fluidized mass through said primary conduit to afirst splitter device,

(f) dividing said fluidized mass in said splitter device into twosubstantially equal and separate streams, (g) transporting each of saidseparate streams as a fluidized mass through a separate secondaryconduit to a second splitter device,

(h) dividing each of said streams into tWo separate smallersubstantially equal substreams,

(i) transporting each of said separate substreams through a tertiaryconduit to a third splitter device,

(j) dividing each of said substreams into two separate substantiallyequal smaller substreams,

(k) transporting each of said separate smaller substreams through feedconduits to the tuyere zone of said blast furnace, and

(l) introducing said separate smaller substreams from said feed conduitsinto different quadrants of said blast furnace tuyere zone.

5. Apparatus for selectively injecting particulate material intopreselected portions of a metallurgical furnace comprising (a) a feederdevice,

(b) means to supply a conveying air stream at superatmospheric pressureto said feeder device,

(0) said feeder device operable to admix preselected quantities ofparticulate material with conveying air supplied thereto to entrain saidcoal particles in said conveying air stream as a fluidized mass of saidparticulate material suspended in said conveying air,

(d) conduit means to convey said fluidized mass to said metallurgicalfurnace,

(e) said conduit means including a first splitter means to divide saidfluidized mass into more than two substantially equal streams, secondsplitter means to divide said streams into substantially equalsubstreams While said particulate material remains suspended in saidconveying air streams, and third splitter means to further divide saidsubstreams into smaller substreams While said particulate materialremains suspended in said conveying air stream,

(f) said conduit means having a plurality of separate outlets arrangedaround the periphery of said metallurgical furnace for injectingseparate streams of said fluidized mass into different portions of saidmetallurgical furnace, and

(g) valve means in said conduit means to close preselected portions ofsaid conduit means to thereby inject streams of said fluidized mass intopreselected portions of said metallurgical furnace.

6. Apparatus for selectively injecting particulate material intopreselected portions of a metallurgical furnace as set forth in claim 5which includes (a) other conduit means connected to said first con duitmeans between said valve means and said outlets, said other conduitmeans operable to supply a gas to portions of said first named conduitmeans to purge said first conduit means of said particulate material.

7. Apparatus for selectively injecting coal particles into preselectedcircumferential portions of a blast furnace tuyere zone comprising (a) acoal feeder device,

(b) means to supply a conveying air stream at superatmospheric pressureto said coal feeder,

(c) said coal feeder operable to entrain preselected quantities of coalparticles in said conveying air supplied thereto as a fluidized mass ofsaid coal particles suspended in said conveying air,

(d) conduit means to convey said fluidized mass to said blast furnace, 1

(e) said conduit means including splitter means to divide said fluidizedmass into more than two substantially equal streams, second splittermeans to divide said streams into substantially equal substreams Whilesaid particulate material remains suspended in said conveying airstreams, and third splitter means to further divide said substreams intosmaller substreams while said particulate material remains suspended insaid conveying air stream,

(f) said conduit means having a plurality of separate outlets arrangedaround the periphery of said blast furnace tuyere zone for injectingseparate streams of said fluidized mass into different portions of saidblast furnace tuyere zone,

(g) valve means in said conduit means to close preselected portions ofsaid conduit means to thereby inject streams of fluidized mass intopreselected circumferential portions of said blast furnace tuyere zone,and

(h) means to control the quantity of coal fed to said conduit means andthe rate of floW of conveying air introduced into said conduit means tothereby regulate the amount of coal particles injected into preselectedcircumferential portions of said blast furnace tuyere zone.

References Cited by the Examiner UNITED STATES PATENTS 432,280 7/1890Nenninger 26628 X 2,279,399 4/1942 Hogberg et a1. 266-28 X 3,116,14312/1963 Reichl 7542 3,150,962 9/1964 Pearson 7542 3,178,165 5/1965Zimmerman 7542 HYLAND BIZOT, Primary Examiner.

20 DAVID L. RECK, Examiner.

H. W. TARRING, Assistant Examiner.

1. A METHOD OF INJECTING KPARTICULATE COAL PARTICLES INTO THE TUYEREZONE OF A BLAST FURNACE WHICH COMPRISES (A) SUPPLYING PARTICULATE COALTO A COLA FEEDER, (B) SUPPLYING A CONVEYING AIR STREAM ATSUPERATMOSPHERIC PRESSURE TO SAID COAL FEEDER, (C) ADMIXING SAIDCONVEYING AIR STREAM AND SAID COAL PARTICLES IN SAID COAL FEEDER TOENTRAIN COAL PATICLES IN SAID CONVEYING AIR STRTEAM AS A FLUIDIZED MASSOF SAID COLA PARTICLES SUSPENDED IN SAID CONVEYING AIR STREAM, (D)INTRODUCING SAID FLUIDIZED MASS INTO A PRIMARY CONDUIT AT A SUFFICIENTVELOCITY TO MAINTAIN SAID COAL PARTICLES SUSPENDED IN SAID CONVEYING AIRSTREAM, (E) TRANSPORTING SAID FLUIDIZED MASS THROUGH SAID PRIMARYCONDUIT TO A FIRST SPLITER DEVICE, (F) MAINTAINING SAID JPARTICULATECOAL ENTRAINED IN SAID CONVEYING AIR STREAM AS A FLUIDIZED MASS IN SAIDFIRST SPLITTER DEVICE, (G) DIVIDING SAID FLUIDIZED MASS IN SAID SPLITTERDEVICE INTO TWO SUBSTANTIALLY EQUAL AND SEPARAT STREAMS, (H)TRANSPORTING EACH OF SAID SEPARATE STREAMS AS A FLUIDIZED MASS THROUGH ASEPARATE SECONDARY CONDUIT TO A SECOND SPLITTER DEVICE. (I) MAINTAININGSAID PARTICULATE COAL ENTRAINED IN SAID CONVEYING AIR STREAM AS AFLUIDIZED MASS IN SAID SECOND SPLITTER DEVICE,, (J) DIVIDING EACH OFSAID STREAMS INTO TWO SEPARATE SMALLER SUBSTANTIALLY EQUAL SUBSTREAMS,(K) TRANSPORTING EAC OF SAID SUBSTREAMS THROUGH A TERTIARY CONDUIT TOTHE TUYERE ZONE OF SAID BLAST FURNACE, AND (L) INTRODUCING SAID SEPARATESUBSTREAMS FROM SAID TERTIARY CONDUITS INTO DIFFERENT QUADRANTS OF SAIDBLAST FURNACE TUYERE ZONE.
 5. APPARATUS FOR SELECTIVELY INJECTINGPARTICULATE MATERIAL INTO PRESELECTED PORTIONS OF A METALLURGICALFURNACE COMPRISING (A) A FEEDER DEVICE. (B) MEANS TO SUPPLY A CONVEYINGAIR STREAM AT SUPERATOMOSPHERIC PRESSURE TO SAID FEEDER DEVICE, (C) SAIDFEEDER DEVICE OPERABLE TO ADMIX PRESELECTED QUANTITIES OF PARTICULATEMATERIAL WITH CONVEYING AIR SUPPLIED THERETO TO ENTRAIN SAID COALPARTICLES IN SAID CONVEYING AIR STREAM AS A FLUIDIZED MASS OF SAIDPARTICULATE MATERIAL SUSPENDED IN SAID CONVEYING AIR, (D) CONDUIT MEANSTO CONVEY SAID FLUIDIZED MASS TO SAID METALLURGICAL FURNACE. (E) SAIDCONDUIT MEANS INCLUDING A FIRST SPLITTER MEANS TO DIVIDE SAID FLUIDIZEDMASS INTO MORE THAN TWO SUBSTANTIALLY EQUAL STREAMS, SECOND SPLITTERMEANS TO DIVIDE SAID STEAMS INTO SUBSTANTIALY EQUAL SUBSTREAMS WHILESAID PARTICULATE MATERIAL REMAINS SUSPENDED IN SAID CONVEYING AIRSTREAMS, AND THIRD SPLITTER MEANS TO FURTHER DIVIDE SAID SUBSTREAMS INTOSMALL ER SUBSTREAMS WHILE SAID JPARTICULATE MATERIAL REMAINS SUSPENDEDIN SAID CONVEYING AIR STREAM, (F) SAID CONDUIT MEANS HAVING A PLURALITYOF SEPARATE OUTLETS ARRANGED AROUND THE PERIPHERY OF SAID METALLURGICALFURNACE FOR INJECTING SEPARATE STREAMS OF SAID FLUIDIZED MASS INTODIFFERENT PORTIONS OF SAID METALLURGICAL FURNACE, AND (G) VALVE MEANS INSAID JCONDUIT MEANS TO CLOSE PRESELECTED PORTIONS OF SAID CONDUIT MEANSTO THEREBY INJECT STREAMS OF SAID FLUIDIZED MASS INTO PRESELECTEDPORTIONS OF SAID METALLURGICAL FURNACE.